Croft



4 SheetsSheet 1.

.(No Model.)

J. S. BANOROFT. TOOL GRINDING MACHINE.

Patented Spt. 29, 1891.

W/T/VESSES:

(No Model.) 4 Sheets-Sheet 2.

J. S. BANCROFT. TOOL GRINDING MACHINE.

y. SMMM WITNESSES:

m: uonms PETERS co.. PNOTO-LITHBL, WASHINOTDN, A! c4 (No Model.) 4Sheets-Sheet 3.

J. S. BANCROI'T.

TOOL GRINDING MACHINE. No. 460,496. Patented Sept. 29, 1891.

m5 Nomus r'nzns cm. PHOTO-LYING" wAsHmGTON, n, c.

UNITED STATES PATENT OFFICE.

JOHN SELLERS BANCROFT, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO THEWVILLIAM SELLERS & COMPANY, INCORPORATED, OF SAME PLACE.

TOOL-GRINDING MACHINE.

SPECIFICATION forming part of Letters Patent No. 460,496, datedSeptember 29, 1891.

Application filed May 12, 1887.

To all whom it may concern:

Be it known that I, JOHN SELLERS BAN- CROFT, of the city and county ofPhiladelphia, and State of Pennsylvania, have in vented certain new anduseful Improvements in Tool- Grinding Machines, of which improvementsthe following is a specification.

My invention relates to machines for forming by grinding the faces andcutting-edges of cutting-tools used on machine-tools. In order toproduce the best output from machine tools in the two essentials ofquality and quantity, the shape of the cutting-tools which remove thematerial is an exceedingly important factor. In most shops the shapes ofthese tools have been and are left to the judgment of the individualoperator, with the result that few, if any, tools in such shops are madein the best shapes. Machines have been made for many years for thepurpose of grinding some forms of cutting-tools mechanically; but noneof them have come into general use, either because they were toolimitedin their range or because, as has generally been the case, theywere constructed in defiance of the underlying principle that shouldgovern all grinding-machines for cuttingtoolsnamely, that the area ofcontact between the grinding-surface of the wheel and the face of thetool should be so narrow as to approximate a mathematical linethat is,length without breadth. Machines heretofore in use have been providedwith compound slide-rests, 011 which the tool to be ground was clampedand by which it could be presented to the abrading-face of the wheel andtraversed across it, the motions of the slide-rests being one parallelto and one at right angles to the axis of the wheel, and whether thetool was ground on the cylindrical face or the plane side of thegrindingwheel the result was in most cases the samenamely, that the faceof the tool was gradually made to conform to the shape of theabrading-surface, and as the surface in coni tact increased the rate ofabrasion decreased and the heating effect increased until after acertain increase of surface all abrading action was converted intoheating action, to the manifest ruin of the tool, the only remedy insuch machines being to change the position Serial No. 237,986. (Nomodel.)

of the tool on the rest, so as to present a new and smaller surface.

It is an object of my present invention to provide means forrapidlyandeconomically forming, by grinding, the working faces of metalcutting-tools.

It is a further object of my invention to provide means whereby thesefaces can be accurately located with reference to each other and to theshank of the tool; and to these ends my invention consists in providinga grinding-wheel with two convex abradingsurfaces, preferably at rightangles to each other, in combination with two slide-rests with theirrespective lines of traverse parallel to the convex abrading-surfaces ofthe grinding-wheel; and it further consists inarrangingarotatabletool-holdingchuckinwhich thetool to be ground isclamped, so that it can be rotated and secured at any desired'angle ofrotation about the axis of the chuck, and in moving this chuck in a lineparallel to the plane of rotation of a grinding-wheel; and it furtherconsists in arranging a slide-rest to move in a line parallel to theplane of rotation of a grinding-wheel and in connecting to this sliderest a supporting-bearing for this chuck, which rotates about an axis atright angles to the axis of rotation of the chuck, whereby a face at anydesired angle with the shank of the tool to be ground may be presentedto an abrading-surface of a grinding-wheel; and it further consists incombining with a toolholding chuck two slide-rests arranged so thattheir lines of traverse are respectively parallel to a plane tangent tothe abrading-surface of the grinding-wheel and perpendicular to thisplane, whereby a face of a tool held in the chuck can be brought againstand trav- 9o ersed across the abrading surface of the wheel; and itfurther consists in providing means for moving the two slide-rests thatsupport the rotatable chuck in a line perpendicular to the lines oftheir own traverse and parallel to the plane of revolution of agrinding-wheel; and it further consists in so arranging a water-supplypipe that water can be directed onto the tool being ground in whateverposition the tool maybe placed and too maintained in this relativeposition to the tool during the motion of the vertical sliderest; and itfurther consists in providing this water-supply pipe with universaljoints provided with frictional clamps, whereby the discharging-nozzlemay be instantly adjusted to and maintained in the required position;and it further consists in counter-balancing the vertically-movingweight of the slide-rest by means of a spring, whereby the work ofovercoming the inertia of a counter-weight is avoided and theoperationfacilitated.

In the accompanying drawings, which form part of this specification,Figure 1, Sheet 1, represents an elevation of a machine embodying oneform of my present improvements. Fig. 2, Sheet 9, is a plan view of Fig.1, showing a partial horizontal section through the center of thetool-holding chuck on the line 00 cc of Fig. 3. Fig. 3, Sheet 3, is anelevation at right angles to and from the right of Fig. 1, but on alarger scale, showing a vertical section through the slide-restsand'chuck on the line :2 y of Fig. 1. The lower part of the frame andthe vertical slide-rest are shown broken to bring the rockshaft andconnections onto the sheet. Fig. 4, Sheet 4, represents a sectionalelevation of the jointed water-supply pipe with the means for moving itin unison with the vertical slide-rest. Fig. 5 is a plan view of thejointed water-pipe. Fig. 6 is a section through the discharge-nozzle onthe line e f of Fig. at.

I prefer to hinge the adjustable toolholding chuck to thesupporting-bearing in order to adapt it to receive a vibratory motion toand from the face of the grinding-wheelthat is, so-that the same machinecan be used for grinding either straight or curved faced tools at will.The details and operation of the devices for grinding curved-face toolsare fully described and shown in a division of this application,numbered 330,450, filed November 15, 1889, and further description hereis deemed unnecessary.

This specification describes a grinding-machine arranged to grind planesurfaces and to form cutting-tools the cutting-edges of which are formedby theintersection of plane surfaces. For the purposeof thisspecification I shall assume that the axis of the grinding-wheel ishorizontal and that the direction in which the tool is traversed past agrinding-surface of the wheel is vertical, and I shall designate theplane which is tangent to a grinding-surface of the wheel as a tangentplane.

The grinding-wheel A, Figs. 1, 2, and 3, is secured upon a mandrel a,journaled in a bearing 1), adjustable on the main frame B, in order thatthe abradiug-surfaces of the wheel may be kept in nearly the sameposition relatively to the tool-holding mechanism. The wheel A is drivenin the usual way by a pulley c, secured to the mandrel a. The grinding-wheelA is formed with two convex abrading-surfaces e 6, preferably atan angle of forty-five degrees with the axis of the wheel and at anangle of ninety degrees with each other, or, geometrically, the wheel Ais formed of two frnstums of similar right cones joined at their bases,the rectilinear elements of the cones forming an angle of ninety degreeswith each other. Two of the rectilinear elements which lie in thehorizontal plane of the axis of the cones are indicated by the brokenlines pdpd, Fig. 2, which lines are also the projections of the tangentplanes, hereinbefore de scribed, of the grinding-surfaces of the wheelA, being the projection of the line of intersection of these tangentplanes. This double truncated cone presents two convex grindingsurfacese and 6', giving the advantage of two abrading-surfaces at right angleswith each other, neither of which is a plane surface, so that eithersurface can be used, as may be most convenient.

In this specification the term convex is not used in its limited meaningof spherically protuberant, but is used in its broader sense, signifyingany exteriorly-cu rved surface, such as, for instance, the roundedsurface of a cylinder or cone.

The tangent planes pd andpcl make equal angles with the axis, so thatthe convex surfaces 6 and e are similar, and the wheel A can be reversedon the arbor in any convenient way, so as to equalize the wear due tothe different amount of use to which the two surfaces may be subjected,which advantage could not be obtained if the angles were unequal.

D, Fig 1, 2, and 3, represents a chuck for holding tools on which planefaces are to be ground. It has a square or rectangular hole through itand is provided with set-screws g g, passing through from the outsideinto the hole perpendicular to each other and to the sides of the hole.The tool to be ground is inserted in this chuck and clamped against itsbase and one side or its base alone by means of these set-screws. If thetool is much smaller than the hole, it is sometimes convenient to use apacking-piecesuch as h-to avoid unnecessary length of the set-screws;but it is not essential that the tool should be in the center of thehole. The chuck D is provided with a journal the axis of which isparallel to the two sides of the square hole against which the tool isclamped, which journal rotates freely in a corresponding horizontalbearing in the adjustable supporting-bearing N, but can be firmly fixedat any desired point of this rotation by the set-screw i. A ring K,secured firmly on the journal of the chuck D, is provided with suitablegraduations, (preferably divided into three hundred and sixty degrees,)and an index a, Fig. 2, is made to correspond with the zero when thebase of the tool is horizontal. This index is provided with a Vernierfor fine adjustment, when required.

The bearing N is fitted upon the slide-rest E and can be swung about thepivot-pin 9 in a horizontal plane through any desired are, which in theconstruction shown, with the two convex surfaces of the grinding wheelat lead to confusion.

ninety degrees with each other, need not exceed one hundred degrees. Thebearing N can be clamped at the desired point by the bolt m, the head ofwhich fits in the circular T-slot m in the slide-rest E. The pin 9 issecured in the slide-rest E and fits easily in a socket in thesupporting-bearingN and serves as an axis about which the bearing can beswung. It is desirable to have this axis as near the end of the toolwhere the faces are to be ground as circumstances will permit, in orderthat these faces may change their position as little as possible withrelation to the grinding-wheel in the various adjustments, and thusavoid an unnecessary amount of motion of the slide-rests to bring thefaces in contact with the grinding-wheel. The circular T-slot m isconcentric with the pin 9. The slide-rest E is provided with a flange n,the arc of which is concentric with the pin 9 and is graduated indegrees. The adjustable supporting-bearing N is provided with an indexand vernier n, adjoining the flange n, and when this index coincideswith the point of the graduations on the flange n the horizontal axis ofthe chuck D is parallel with the tangent plane pd and perpendicular tothe other tangent plane pd. If the tangent planes were at any otherangle than ninety degrees with each other, it would be necessary to havetwo sets of indices or graduations, one for each plane, which might Thegraduations may be upon the adjustable bearing N and the index on theflange n, if preferred.

The slide-rest E can be moved across the top of the slide-rest l in ahorizontal plane by means of the screw 10 in a direction parallel to thetangent plane pd. The Slide-rest E can be moved across the top of thevertical slide-rest F in a horizontal plane by means of the screw 11 ina direction at right angles to that of the slide-rest E and parallel tothe tangent plane pd.

The vertical slide-rest F, Figs. 1 and 3, can be moved up and down in avertical line parallel to the plane of rotation of the grindingwheel,and also parallel to the line of intersection of the tangent planes pdand pd, sliding in a bearing b, carried by the main frame B of themachine. Near the lower end of the vertical slide-rest F is secured astud c, to which is journaled one end of a linkj, the other end of whichis hinged by means of the pin n to the bell-crank lever G, which iskeyed to the rock-shaft 12, the journals of which are carried by thebearings q and q in the main frame B. The lever G is made in the form ofa bell-crank with the arms in different planes, connected by the hub Gin Fig. 3. To the lower arm G is attached the spring H, the other end ofwhich is secured by means of the adjusting-bolt 13 to a projection 14from the main frame B, and is adjusted so as to counterbalance theweight of the vertical slide-rest F and the parts it carries at themiddle of its stroke. As the sliderest F is moved down the spring H isextended, and its action is to retard the motion of the rest, and bythus overbalancing the weight of the slide at the bottom of the strokethe return is made easier. The diminished tension of the spring at thetop of the stroke underbalances the rest, the weight of which tends toarrest its motion upward and assist its return, thus facilitating theoperation and avoiding the inertia resulting from the use of an ordinarycounter-weight. The spring H will always return in contracting as muchpower as it required to extend it, as its ac tion is frictionless, andthe power required to put the vertical slide-rest into oscillation bymeans of the lever J is therefore very slight, and this motion can becontinued by the workman without fatigue. WVith the ordinarycounter-weight the workman has to overcome the inertia at the beginningof each stroke and to check the momentum at the end of the stroke, andthe force required to do this is not available for the return, as withthe spring, and hence is entirely wasted and rapidly fatigues theoperator.

In setting the tool to be ground and in adjusting it to thegrinding-wheel it is desirable that the tool-holding chuck D, which iscarried by the vertical slide-rest F, should be in the horizontal planeof the axis of the grinding-wheel-that is to say, midway in the verticalmovement of the slide-rest. effected by means of the spring H, thetension of which is adjusted to counterbalance the weight of theslide-restF and the parts it carries when in this position.

The rock-shaft 12 has fastened to its end a hand-lever J, which iscurved, as shown, to permit the horizontal swing of the chuck whenholding a long tool which may project through the back of the chuck. Thehandle of the lever is carried up to a place convenient to the hand ofthe operator. The motion of this hand-lever J forward and backwardimparts the up-and-down motion to the vertical slide-rest F, thuscarrying a tool held in the chuck up and down across theabrading-surface of the wheel.

The operation of grinding a tool with plane faces is as follows: 0,Figs. 1, 2, and 3, represents a tool whose cutting-edges are formed bythe intersection of four planes. \Vhen this tool is doing work in thelathe, it rests upon its base f, and in order to obtain the best resultsthe planes which form the cutting-edges should make certain definiteangles with this base and with each other. This tool is clamped in thechuck D with its base resting on that side of the square hole which isintended to receive it, or on a parallel packing-piece h, as shown. Ifthe zero of the graduations on the chuck coincides with the index, thebasefof the tool will be horizontal. If new the adjustable bearing N isswung about its vertical axis, so as to bring the 90 point of itsgraduations to coincide with the index and is clamped there, the toolwould be in the position shown This is ITO in Figs. 1, 2, and 3. Theside face of the tool would, if ground in this position, form a planeperpendicular to its base and would not have any clearance, to obtainwhich the chuck I) must be rotated about its axis the required number ofdegreessay three degrees-and be held there by the set-screw z', thegraduations on the ring K definitely indicating the angle of rotation.By operating the horizontal slide-rests E and E the side face of thetool can be brought to touch the grinding-surface e. The verticalslide-rest F is then moved up and down by operating the hand-lever J,thus carrying the tool O past the grinding-surface e and touching itonly on the line pd of the tangent plane and fulfilling the conditionsrequired for the greatest efficiency in grinding, the slide-rest Efeeding the tool against the wheel as the tool is ground away and theslide E being used to change the position of the tool from time to timeto prevent grooving. The surface ground on the tool will be parallel tothe tangent plane pd and to the line of'traverse of the verticalslide-rest F. The opposite side is ground in the same way after rotatingthe chuck D half-way round and setting to the angle of clearancerequired. To grind the top face, the set-screw 'i is released, the chuckD rotated until the index points to the required angle-say ninetydegreesand the tool again brought in contact with the grinding-surface.lVhen the top has been finished, the end can be ground by presenting itto the grinding-surface e of the wheel, the desired clearance beingobtained by moving the adjustable bearing N about its vertical axis 9until the desired angleis obtained, in every case the face to be groundbeing traversed past the abradingsurface by means of the verticalslide-rest F, the four planes forming the cutting-edges being groundwithout removing the tool from its chuck D, and consequently all of thefaces will have definite relations to each other and to the base of thetool.

If a parting-tool is to be ground having its shank at an angle or bent,the operation of grinding is the same as before, excepting that most ofthe faces have to be presented to the grinding wheel by using theadjustments about both the vertical and horizontal axes, the positionrequired being determined by calculation or by the use of agonion1eter,and then recorded in a table for future use.

The slide-rests E and E are used in conjunction to bring any face of atool in contact with the appropriate grinding-surfaee of the wheel, andthen the movement parallel to that surface is used to traverse thetool-face along the grinding-line to keep it straight and true andprevent the grinding of ridges in the toolface. If the bearing N be setso that the zero of its graduations coincides with the index, and theslide-rest F be adjusted vertically until the axis of rotation of thechuck D is in the plane of the axis of the grinding-wheel,

and if the chuck D be rotated while a tool held in it touches thegrinding-surface c, then the tool will be ground to a cylindrical shape,the radius of which will be the distance from the axis of the chuck tothe grinding-surface. If the bearing N be set at an angle, the tool willbe ground to a conical shape. In these cases, however, the axes of thecylinder and cone will be parallel with the side of the tool instead ofperpendicular to it, as is generally required in practice, for whichpurpose the shank of the tool must be clamped or secured at right anglesto the axis of the chuck I).

The main frame Bis provided with or formed in the shape of a tank, asshown, to provide a reservoir for the water used in keeping the toolcool. To supply the water,I use a pump of any suitable kind driven asmay be most convenient, and to its discharge-pipe I attach one end of aflexible hose 70, the other end of which is attached to and dischargesinto a system of adjustable pipes'provided with a discharge-nozzle 71.(Shown in section in Fig. 6.) This nozzle is provided with a trunnionturning freely in its bearing 72, secured to the end of the pipe 73. Thetrunnion is perforated, as shown, so as to allow water from the pipe 73to flow freely through it to the nozzle 71. The upper end of the pipe issecured to the ball 74, which fits into a spherical recess provided inthe casting 7 5, secured on the end of the pipe 76. A clamp 77, whichfits the ball 74, serves to hold the ball 74 to its seat and preventsleak of the water and gives sufficient friction to hold the pipe 73 inany required relation to the pipe 76, while permitting easy adjustmentby hand. The other end of the pipe 76 is provided with a socket 78 andclamp 79,by which it is held to place on the ball 80, secured to a pipe81, connected with the discharging end of the hose 7 O. Theadjustable-pipe system is preferably counterbalanced, as shown, by aweight 82, carried by a rod secured to the casting 78. Theadjustable-pipe system is carried by a rod 83, which is guided near itsupper end in a bearing Sat, secured to the main frame 13, and its lowerend is carried by a lever 85, of the same length as the lever G andsecured to the same shaft 12, whereby the rod 83 is moved in unison withthe vertical slide F, so that when the nozzle 71 is set so as to deliverwater in the proper relation to a tool being.

loo

TIO

formed of two frustums of cones joined at their bases and twoslide-rests, each of which has a traverse parallel to anabrading-surface of the wheel,in combination with a toolholding chuck.

2. In a tool-grinding machine, a grindingwheel with twoabrading-surfaces formed of two frustums of cones joined at their bases,in combination with two slide-rests, each of which has a traverseparallel to an abradingsurface of the wheel and a traverse, common toboth, parallel to the plane of rotation of this wheel.

3. A grinding-wheel provided with two abrading-surfaces formed of twofrustums of cones joined at their bases, in combination with atool-holding chuck rotatable about its axis and a supporting-bearingrotatable about an axis at right angles to that of the chuck andparallel to the plane of rotation of the grinding-wheel.

4. In a tool-grinding machine, a grindingwheel, in combination with atool-holding chuck rotatable about an axis, with an interiorclamping-surface parallel to this axis, upon which the tool to be groundmay be secured, and a supporting-bearing for said chuck adjustable aboutan axis at right angles to that about which the chuck is rotatable.

5. In a tool-grinding machine, in combination, a tool-holding chuck, asupporting-bearing in which the chuck may be rotated and secured at anyangle of rotation, a slide-rest which supports and moves the saidhearing at right angles to the axis of the chuck and parallel to theplane of rotation of the grinding-wheel, and mechanism for regulatingthe distance between the chuck and the grinding-wheel.

0. In a tool-grinding machine, a slide-rest which moves parallel to theplane of rotation of the grinding-wheel, a supporting-bearing I which isadjustable about an axis parallel to the plane of rotation of thegrinding-wheel, and mechanism for regulating the distance between thissupporting-bearing and the grinding-wheel, in combination with atoolholding chuck rotatable about an axis at right angles to that of thesupporting-bearing.

7. In a tool-grinding machine, a grindingwheel, in combination with atool-holding chuck rotatable about an axis approximately parallel to thetool which it holds, with mechanism for securing it at any angle ofrotation, and a supportingbearing for said chuck adjustable about anaxis at right angles to that of the chuck, with mechanism through whichthis bearing is supported and moved in two planes, one parallel to aplane tangent to the grinding-surface of the wheel and the other atright angles thereto.

8. In a tool-grinding machine, a grinding- -wheel, in combination with atool-holding chuck rotatable about its axis, a supportingbearingadjustable about an axis at right angles to that of the chuck andparallel to the plane of rotation of the grinding-wheel, and threeslide-rests which support and move this bearing in three lines, each ofwhich is at right angles to the other two.

9. In a tool-grinding machine, a grindingwheel, a tool-holding chuck,and a system of slide-rests, in combination with an adjustablewater-supply pipe connected to the movable parts of the slide-rest,which moves parallel to the plane of rotation of the grinding-wheel.

10. The combination of a grinding-wheel, a vertically-movable slide-restthat moves parallel to the abrading-face of the wheel, and an adjustablewater-supply pipe movable with the slide-rest and provided with aballjoint at its discharging end.

11. In a tool-grinding machine, a tool-holding chuck, a verticalslide-rest, and mechanism substantially as described between the chuckand the vertical slide-rest, in combina tion with mechanism whichoperates to return these parts to a midway position in their verticaltraverse whenever they are removed therefrom.

CHAS. E. PANcoAsT, JOHN L. PHILLIPS.

